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Questions tagged [disk-cache]

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How can I disable caching for the volume in Windows 2012?

When I try to disable disk cache on Windows Server 2012, I get "windows could not change the write-caching setting for the device" error. How do I disable the disk cache?
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0answers
15 views

How do I go about limiting data sent/received on a NIC

I have a virtual pfSense in HYPER-V on my windows 10 PRO. I am using 2 Addon NICS which 1 of them is a Mobile Data connection. The Other is an unlimited Cable plan, at 4pm the internet slows so badly ...
3
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1answer
612 views

How to ensure HDD Write Caching is disabled on MS Storage Spaces

I have a Storage Spaces pool on a server that is not currently power protected. It consists only of mechanical hard drives. I want to compare performance of write caching enabled vs disabled so I can ...
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0answers
125 views

Debian max_ratio setting for device not working

My debian 8 machine has 2 drives. Sometimes I move/copy files from drive A to drive B. Drive B is slow, so the file system cache is full causing the system to be slow/unresponsive when copying large ...
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1answer
75 views

Questions about Varnish file storage engine

I have Varnish cache in front of some websites with the following storage engine configuration: Storage: file Size: 130GB The server where it is installed has the following configuration: RAM: 7.5 ...
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2answers
159 views

MySQL slow, but speed up after drop disk caches

I have very busy Linux MySQL server with huge database. Server usually work on load average 2 or less. The server have software raid (mdadm) that is currently rebuilding. Several times today, MySQL ...
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3answers
106 views

Confused by write cache flags

I'm looking to maximise performance of my hard drive by enabling write caching. I understand the risks in doing this, but believe them to be insignificant for how I will use it. On the HD Properties ...
13
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2answers
932 views

How to setup an NFS server that caches a network share?

User data is stored on two fairly large (>1 PB) OpenStack Swift storage clusters. Let them be Cluster A and Cluster B. In addition, there are several PoPs that need to interact with that data. ...
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2answers
1k views

Windows Server virtual disk cache settings

In Windows under Azure or Hyper-V, the Disk Policy write cache settings for a virtual disk will always appear to be enabled from the server configuration, regardless of the actual status of write ...
3
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1answer
518 views

Linux - Disk / Filesystem as a LRU Cache (with transparent expiry)

I have a case where I'd want to use local disk as a LRU cache for (hot) files from a separate web service (something like S3). If the file doesn't exist on disk, the file is read over the internet, ...
1
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2answers
577 views

Why would diskspd perform better without cache?

We are currently investigating high disk latency on a Windows server 2012 r2 that run as an SQL server. It is a virtual machine under VMware and the datastore of the faulty disk is linked with a very ...
2
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2answers
278 views

Active process swapping despite free memory

For some reason our system starts swapping (actively used memory) at around 60GB used memory. (see edit below, it seems I/O and disk cache usage, even of previously run processes has an effect) ...
1
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1answer
809 views

Windows Server 2012 write caching

From MSDN: By default, Windows caches file data that is read from disks and written to disks. [..] Caching is managed per file object. The policy of delaying the writing of the data to the file and ...
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0answers
459 views

Disable nginx fastcgi_cache when disk is full

When there is no disk space, nginx is still able to work correctly. It can serve static files, and it can pass the request to a fastcgi server (such as PHP), and it can serve the dynamic response to ...
1
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2answers
1k views

Are bcache and/or dm-cache considered stable for production in 2016?

I would like to use linux SSD caching (dm-cache or bcache) with Debian Jessie production servers. (kernel 3.16) My question: Are dm-cache and bcache modules reliables in linux 3.16 ? Do I need to ...
1
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1answer
625 views

What is the “right way” to combine sync and drop_caches?

When I need to do echo 3 > /proc/sys/vm/drop_caches with a sync beforehand, is it better to use sync && echo 3 > /proc/sys/vm/drop_caches or sync ; echo 3 > /proc/sys/vm/drop_caches....
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2answers
832 views

How to increase the disk write buffer for rsync on Mac OS X?

I have to copy some TB of data from one external drive to another (mostly ~400 MB files). The source is NTFS-formatted USB2 and the best read speed I can get from it is 7MB/s. The target is HFS+ USB3 ...
3
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1answer
2k views

Disable file cache for mount point

I ran into a bug similar to this one: RHEL NFS client returns NULL bytes when reading a growing file So my solution was to check for \0 Bytes and reread the file. Problem here is, that the wrong ...
1
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1answer
1k views

Apache when to use mod_cache? disk_cache vs memory_cache?

I'm making use of Apache 2.4.10 on Ubuntu 15.04 and my entire server runs on a SSD and is virtualised in Hyper-V. When should I enable mod cache in Apache 2.4? Currently I have pretty good TTFB for ...
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2answers
35 views

8x slower cat for the same files on the same disk but different directory

I'm having an issue where I have 8x slower access to a set of files as compared to the same files in another directory on a linux machine. The filesystem is a 36TB RAID-5 filesystem exported from a ...
2
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3answers
676 views

Would the data on the RAID Card Cache and Drive Cache be lost when a kernel panic happens?

Is a BBU necessary when you have A+B power? Would the data on the RAID Card Cache and Drive Cache be lost when a kernel panic happens and you are forced to do a cold reset?
2
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1answer
178 views

Linux filesystem page cache - hot or not

How can you tell how much of the filesystem cache is hot (frequently accessed) or not? The use case would be determining when you are approaching the limits of your memory but before you actually hit ...
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1answer
557 views

Can high disk cache usage lead to external fragmentation and ultimately to page allocation failures?

We're getting page allocation failures on a Linux server (3.2 kernel). We've been told the problem is directly related to the high use of the memory for cache; this would lead to external ...
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1answer
2k views

Linux read disk cache and NFS

I am interested in the impact of the read disk cache on accessing a file through NFS. Lets say I have a file on NFS. I access it (do "cat myfile") from a linux host "A". If there's enough RAM a file ...
3
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1answer
1k views

On a system with 64GB mem the Linux Buffer run full while copying with dd to dev null and io stops till manual drop_caches

I am running a server with linux software raid 10. It is a dual CPU system with 64GB Ram. 2x16GB dimms related to each of the CPUs. I want to use dd to backup kvm virtual machines and run into a ...
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1answer
4k views

Why is mongod not using all available RAM?

We have an mongod instance runnning on a VM, and it doesn't seem to be using all available memory. It's page-faulting significantly more than usual, and the system's performance has been significantly ...
0
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1answer
260 views

Linux not freeing the file buffer when we execute rm or > (redirection) operator

I have one router which has embedded-linux with kernel version 2.4.22 running on it. I know its very old version but i have to deal with it. Please take a look at the free command output when i run it ...
0
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1answer
361 views

nginx proxy_cache or Memcached

I currently use nginx's proxy_cache for file-based caching in front of three Django applications (Apache/mod_wsgi). For some locations/URLs, I disabled proxy_cache and used Memcached (per view) within ...
1
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1answer
525 views

ram disk mirroring part of physical disk

What I would like to do/have is: Some kind of application/driver that creates a RAM drive/partition that is actually assigned a drive letter (eg. D:). This drive letter should be based on/mirroring a ...
4
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2answers
2k views

Write caching in linux

I have read a lot on serverfault and searched on google about write caching, but still cant find the answer. I have an HP ProLiant DL380 G5 with HW raid with 512 MB Battery backed cache. I use debian ...
1
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1answer
435 views

Apache mod cache mem/disk saves the cache for 10 seconds and than re-cache

I have this set up in my 000-default: <VirtualHost 192.168.1.10:80> ServerName live.website.com DocumentRoot /var/www/live.website.com SetOutputFilter INFLATE;proxy-html;DEFLATE ...
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2answers
2k views

Safety of write cache on SATA drives with barriers

I've been reading lately about write caching, NCQ, firmware bugs, barriers, etc regarding SATA drives, and I'm not sure what's the best setting that would make my data safe in case of a power failure. ...
3
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1answer
71 views

varnish delete least requested files

I see that varnish can be configured to set -smalloc or -sfile with a certain size. I want to set a file cache of 1G such that least requested files are deleted first when cache is full. Is this ...
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0answers
240 views

Disk cache (write back) disables automatically

some days ago I discovered (using Munin) that my server had high iowait times. The reason was that write cache was disabled. I enabled it using hdparm -W1 /dev/sda but after some time (ramdonly) it ...
3
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1answer
1k views

Solaris 10: Drop disk cache? (to benchmark app)

Is there a command to drop the ZFS and UFS disk caches? (Preferably just one folder hierarchy.) I'm trying to tuning the performance settings of an application that read/writes data from a large ...
2
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1answer
110 views

CentOS VM only using a third of available memory

I have a VM slice running CentOS, on Parallels. Here is the output of free -m [root@server ~]# free -m total used free shared buffers cached Mem: 960 ...
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3answers
16k views

Should I disable write caching on my Windows 2008 VM?

I have a Windows Server 2008 x64 Standard virtual machine that runs on a machine with a hardware RAID controller, a Perc 6/i, which has a battery on-board. Doing everything I can for additional ...
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4answers
3k views

Would a PHP application benefit from being served from a RAM drive?

I am in charge of hosting a PHP application that is large and slow, but easy to scale. The application is entirely static, with writable disk storage needed. We've profiled the application, and the ...
2
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3answers
3k views

High disk I/O activity in CentOS server

I have about 16 websites in a CentOS dedicated, and I am having some problems on high traffic hours, it seems to be a high disk I/O activity causing a general slowdown. I've installed atop and this ...
0
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1answer
870 views

Which Linux filesystem is best for a huge Apache mod_disk_cache partition?

Talking about a huge (50GB, 500.000 entries) Apache disk_cache partition: Which Linux filesystem performs best for this task? In my example, the partition has a lot (500.000) of very small files (<...
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2answers
23k views

Linux not freeing large disk cache when memory demand goes up

Running Ubuntu on a 2.6.31-302 x86-64 kernel. The overall problem is that I have memory in the 'cached' category that keeps on going up and will not be freed or used even when our application needs it....
0
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1answer
959 views

Linux server with JBoss , the system cache increased each day

We run an Apache Mod_proxy cluster with 3 JBoss in three dedicated server. Because we need share many files (small object files which our apps need to read/write ) between these JBoss servers ,we ...
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3answers
6k views

Why does mdadm write unusably slow when mounted synchronously?

I have a 6 disk raid6 mdadm array I'd like to benchmark writes to: root@ubuntu:~# cat /proc/mdstat Personalities : [raid6] [raid5] [raid4] md0 : active raid6 sda[0] sdf[5] sde[4] sdd[3] sdc[2] sdb[...
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1answer
3k views

How do I see if my disk cache is disabled on Linux?

I have an ubuntu linux virtual machine here and I think there is no disk cache. For example this is the output from free -m: total used free shared buffers ...
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1answer
9k views

What is read cache in “[sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA”?

I'm trying to figure out what the read cache part of the following message refers to: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA Is it "IDE drive's read-...
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1answer
671 views

Raid Caching configuration suggestions

I'm wondering if there's the optimal Cache setting for the following Raid controllers and raid setups. (OS: windows 2008 R2, App: II7, DB: SQL Server 2008 R2 Enterprise) PERC 6/i: (The default ...
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1answer
1k views

How Does The Linux Disk Cache Work With iSCSI and GFS2?

I'm planning to share a GFS2 filesystem via iSCSI to my web servers. Are the files read by my web servers cached locally using the linux disk cache stored in memory or are they only cached on the ...
3
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1answer
2k views

How much does HDD cache matter with Linux softraid?

I'm in a process of renewing/expanding my disk sets, but not quite sure what kind of disks to get, cache-wise. What difference does disk cache amount of 16/32/64MB do, in capacities of, say, 1/1.5/...
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3answers
17k views

Store Varnish cache in hard disk

The situation is: Im building PHP application, and need http caching. Varnish is great, and lots of people tell me that Varnish store the cached data in RAM. But I want it cached in hard disk. Is ...
7
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4answers
9k views

Disable all disk caching for apache2 on linux

For benchmarking purposes I want to force Apache 2 to load each requested file from disk instead of loading it from a cache in memory. From what I have read doing a sync followed by echo 3 > /proc/...